This invention relates generally to a method and means for repairing underground irrigation systems.
More particularly, this invention relates to a repair assembly for broken or leaking risers in an underground irrigation system and to a method for the use of that assembly.
In many parts of the American West, particularly in the Rocky Mountain states and California, it has become common to distribute irrigation water through a system of underground mains and laterals. The mains and laterals are typically constructed of reinforced concrete or Transite pipe with the mains often having an internal diameter of several feet and the laterals ranging downwardly to an internal diameter of six to eight inches. Both mains and laterals are buried deeply enough, usually about two and one half feet, to not interfere with cultivation and to protect against freezing.
Risers are spaced along the distribution lines to allow distribution of irrigation water on the land surface adjacent each riser. The risers are typically constructed of steel pipe, extend vertically from the main or lateral to above the ground surface, and are equipped with an above-ground valve to control water flow. The lower end of each riser is connected to the main or lateral by means of a threaded joint in the pipe wall. Water pressure within the distribution system may range as high as sixty psi.
The mains and laterals have a long service life. However, there is relatively frequent failure of the threaded joint connecting risers to distribution lines. Joint failure is believed to be caused primarily by vibration of high pressure water flowing through the riser and to the surge and hammer occurring during opening and closing of the riser valve. Joint failure results in water leakage which washes out that section of distribution line and requires that the line be closed down for repair.
Ordinarily, joint failure results in the destruction of the threads formed in the distribution pipe wall. Consequently, it is present practice to replace that section of main or lateral containing the riser joint. This practice requires use of a backhoe to excavate along the pipe for a distance upstream and downstream of the riser. A section of pipe, typically some ten to twelve feet in length and containing the riser joint, is then cut out and removed. A replacement pipe section containing a new riser joint is then installed using gasketed flanges to connect and seal each end of the replacement section to the existing pipe ends.
The present techniques for repairing leaking risers are difficult, expensive and require extensive excavation. Up to this time, no practical alternatives to the replacement of a section of distribution line upon riser joint failure have been developed. Hence, it is apparent that a means and method for repair of riser joints without replacement of the distribution line has significant practical benefit.